Erratum in

Sci Rep. 2013;3():1131

Abstract

Sirt1 is an NAD(+)-dependent deacetylase that extends lifespan in lower organisms and improves metabolism and delays the onset of age-related diseases in mammals. Here we show that SRT1720, a synthetic compound that was identified for its ability to activate Sirt1 in vitro, extends both mean and maximum lifespan of adult mice fed a high-fat diet. This lifespan extension is accompanied by health benefits including reduced liver steatosis, increased insulin sensitivity, enhanced locomotor activity and normalization of gene expression profiles and markers of inflammation and apoptosis, all in the absence of any observable toxicity. Using a conditional SIRT1 knockout mouse and specific gene knockdowns we show SRT1720 affects mitochondrial respiration in a Sirt1- and PGC-1α-dependent manner. These findings indicate that SRT1720 has long-term benefits and demonstrate for the first time the feasibility of designing novel molecules that are safe and effective in promoting longevity and preventing multiple age-related diseases in mammals.

Conflict of interest statement

D.A.S. consults for and J.L.E., C.H.W., G.P.V. and P.J.E. are employed by Sirtris, a GSK Company, that has a commercial interest in developing SIRT1 activators.

(a) Kaplan-Meier survival curves of mice fed a standard diet (SD) or a high-fat diet (HFD) supplemented with SRT1720 at either a low (HFD-L) or high (HFD-H) dose. Mean and maximum lifespan in weeks and the hazard ratio for mortality are represented below. In the parentheses the increases in maximum lifespan from birth and then diet onset are given. (b) Body weights of the groups over time, with average caloric intake over the course of the feeding study in the inset. Below are images of representative mice to illustrate phenotypic body mass of the groups at 82 weeks of age. (c) SRT1720 maintained normal liver appearance and reduced the onset of fatty liver as depicted by images of whole livers harvested after 12 weeks on diets and subsequent oil red O staining. Quantification of steatosis was performed by a blinded pathologist on livers from 82 week-old mice (26 weeks on diets; n = 6). Serum levels of the aminotransferases ALT and AST were reduced by SRT1720 compared with HFD (n = 6; age = 82 wks; diet = 26 wks). (d) SRT1720 normalized pancreas morphology as illustrated by immunostaining for glucagon-producing cells (α cells, green) and insulin-producing cells (β cells, red) in islets, and quantification of islet area and relative α-cell and β-cell areas within the islets (n = 8; diet = 12 weeks). Data are represented as the mean ± SEM. *P < 0.0083 from SD; †P < 0.0083 from HFD.

Figure 3. SRT1720 suppresses apoptosis and restores a more normal gene expression profile indicative of reduced inflammation in the livers of mice fed a high-fat diet.

(a) Two indicators of increased programmed cell death, caspase 3 activity and DNA fragmentation, were increased in the HFD compared with SD. This effect was completely blocked by both doses of SRT1720 (n = 6; age = 82 wks; diet = 26 wks). (b) Parametric analysis of gene-set enrichment (PAGE) comparing every pathway significantly upregulated (red) or downregulated (blue) by HFD (as compared with SD, 349 pathways of 1687 considered), and the corresponding effects of the low and high doses of SRT1720 on those same pathways (n = 3; age = 82 wks; diet = 26 wks). (c) The five most highly upregulated and downregulated named genes, based on fold-change in HFD-R compared to HFD (filtering on a false discovery rate of <0.05). (d) Multiple pro-inflammatory markers including TNF, IL-6, IL-1β and iNOS were increased in the HFD mice relative to SD. No significant increase from SD was seen in the HFD-H group, and there was a significant decrease from HFD in the TNF and iNOS expression of the HFD-H livers (n = 6; age = 82 wks; diet = 26 wks). *P < 0.0083 from SD; †P < 0.0083 from HFD.

Figure 5. SRT1720 rescues respiratory capacity in mitochondria from wild type mice treated with a high fat diet but not after Sirt1 knockout.

(a) State 3 oxygen consumption by mitochondria isolated from the liver was reduced by HFD. Treatment with SRT1720 in the HFD was protective only in WT mice. (b) Oxygen consumption during state 4 respiration was unchanged by diet or genetic manipulation. (c) The respiratory control ratio was also reduced by HFD and rescued by SRT1720 only in WT mice, as was FCCP-induced respiration (d). n = 4 mice per group; age = 30–32 weeks; diet = 18 weeks. Data are represented as the mean ± SEM. *P < 0.05 from WT SD, #P < 0.05 from KO SD, &P < 0.05 from WT HFD.